Breast Cancer Causes and Risk Factors

Medically Reviewed by Dr. K on 26 March 2021

While the specific causes of breast cancer remain uncertain, the key contributing factors are well understood. Despite this, the majority of people found to be at increased risk for breast cancer do not develop the disease, although those with no established risk factors do.

The biggest threats include growing older and having a family history of breast cancer. Women with certain forms of benign breast lumps and women who have had ovarian cancer are at a greater risk. If you’ve had breast cancer before, it’s possible to have it again.


What Are the Odds of Developing Breast Cancer?

In 1940, a woman’s average chance of having breast cancer was 5%. Currently, the risk is about 12%. These women have no established risk factors in around half of the cases.

Uncontrollable Risk Factors

Female gender:  Breast cancer may affect men as well, although it is 100 times more likely to affect women.

Family history:  An individual who has had cancer in one breast, such as ductal carcinoma in situ (DCIS) or invasive breast cancer, is three to four times more likely to acquire a new breast cancer in the other breast or another portion of the same breast, which is unrelated to the first one. This is not the same as a recurrence of prior breast cancer.

Age:  Once you get older, the risk increases. Every year, nearly 77% of women diagnosed with breast cancer are over 50, with more than 40% being 65 or older. Breast cancer has a 1 in 68 risks of occurring in women between the ages of 40 and 50. From 50 to 60, the probability rises to 1 in 42. It’s 1 in 28 between the ages of 60 and 70. It’s also 1 in 26 in women aged 70 and above.

Immediate family history:    A woman’s likelihood of breast cancer is increased if she has a mother, sister, or daughter (“first-degree" relative) with breast cancer. If this relative was diagnosed with breast cancer before the age of 50 and had cancer in both breasts, the risk is much higher. Having one first-degree relative with breast cancer almost doubles the chance, and having two first-degree relatives with breast cancer almost triples the risk. The risk also increases if you have a male blood relative with breast cancer.

Genetics:  Inherited breast cancer accounts for around 5% to 10% of all cases. BRCA1 and BRCA2 gene mutation carriers are more likely to develop breast cancer. At the age of 80, women who have an inherited alteration in the BRCA1 gene have a 72% risk of having breast cancer. At that age, an individual with a hereditary mutation in the BRCA2 gene has a 69% risk of developing breast cancer.

Dense breasts: Breast tissue consists of a combination of fatty, fibrous, and glandular tissue. Dense breasts contain less fat and more glandular and fibrous tissue. Breast cancer is 1.5 to 2 times more common in people who have dense breasts.

Lesions of the breast:  A woman’s incidence of breast cancer is increased by four or five times if she has atypical hyperplasia (lobular or ductal) or lobular carcinoma in situ.

Distant family history:  Breast cancer of second- or third-degree families, such as aunts, grandmothers, and cousins, is referred to as this.

A previous abnormal breast biopsy:  Women with fibroadenomas with complicated characteristics: hyperplasia without atypia, sclerosing adenosis, and single papilloma, have a higher chance.

Reproductive history:  Your risk increases with the amount of oestrogen your body has generated over time. Having your period before the age of 12, beginning menopause after the age of 55, and never becoming pregnant, all increase your lifelong hormone exposure and increase the chance of breast cancer.

Radiation treatment: When you received radiation treatments to your chest before the age of 30, generally with tumours like lymphoma.

There is a family history of cancer:  If anyone in your family has had ovarian cancer by the age of 50, the odds are greater.

Heritage:  White and African-American people are more likely than Hispanic, Asian/Pacific Islander, and Native American women to have cancer.

Diethylstilbestrol exposure (DES):  Between 1940 and 1971, several people were given this medication to prevent miscarriage. If you or your mother had it, risks of getting breast cancer are increased.


Controllable Risk Factors

Weight:  After menopause, being overweight raises the chances.

Alcohol:  The consumption of alcoholic drinks has been related to the growth of breast cancer. Women who consume one alcoholic drink a day have a relatively small increase in risk compared to nondrinkers, whereas heavy drinkers (2 to 3 drinks a day) have a 20% higher chance.

Hormone replacement therapy (HRT):  The utilisation of oestrogen and progesterone over an extended period of time increases the likelihood of breast cancer. If you haven’t used them in at least 5 years, the chance seems to be eliminated.

Sedentary lifestyle:  If you do not exercise, the chances of getting cancer increases.

Reproductive history: You’re at a greater chance if you had your first child after the age of 30 or if you’ve never had a full-term birth. So does breastfeeding.


Breast Cancer Causes That Aren’t Related

These factors have little impact on the chances of developing breast cancer:

  • Antiperspirants are used to avoid sweating.
  • Wearing bras with underwires
  • Having a miscarriage or abortion
  • Fibrocystic breast changes (dense breast tissue with benign cysts)
  • Multiple pregnancies
  • Caffeine and coffee
  • Dyeing your hair

Talk to your doctor if you have any concerns regarding your risk of developing breast cancer.


Referenced on 26.3.2021

  2. The American Cancer Society: “Breast Cancer Risk Factors You Cannot Change,” “Disproven or Controversial Breast Cancer Risk Factors,” “How Common is Breast Cancer?” “Lifestyle-related Breast Cancer Risk Factors.”
  3. UCSF Health: “Taking Charge: Who Gets Breast Cancer?”
  4. National Cancer Institute: “Alcohol and Cancer Risk,” “BRCA Mutations: Cancer Risk and Genetic Testing,” “Breast Cancer Risk in American Women,” “Hair Dyes and Cancer Risk,” “Reproductive History and Cancer Risk.”
  5. Medscape: “Breast Cancer in the Elderly,” “Breast Cancer Risk Factors.”
  6. Cancer.Net: “Hereditary Breast and Ovarian Cancer.”
  7. CDC: “What Are the Risk Factors for Breast Cancer?"
    Mayo Clinic: “Fibrocystic breast changes:
  8. Linked to breast cancer?”
  9. Oncology Nutrition: “Caffeine and Cancer.”

Previous Post

Cancer Treatment, Premature Menopause, and Infertility

Next Post

Stage 0 Breast Cancer Treatment Options

Related Posts